You take good care of your pet. But what’s your pet done for you lately? Scared intruders from your door? Fetched your slippers? Given you a loving nuzzle? People have lots of reasons for owning pets. Now a small but growing body of research suggests that owning or interacting with animals may have the added benefit of improving your health.

People and animals have a long history of living together and bonding. Perhaps the oldest evidence of this special relationship was discovered a few years ago in Israel—a 12,000-year-old human skeleton buried with its hand resting on the skeleton of a 6-month-old wolf pup. “The bond between animals and humans is part of our evolution, and it’s very powerful,” says Dr. Ann Berger, a physician and researcher at the NIH Clinical Center in Bethesda, Maryland.

Today animal companions are more popular than ever. The pet population nationwide has been growing dramatically for nearly a half century, from about 40 million pet cats and dogs in 1967 to more than 160 million in 2006. About two-thirds of U.S. households now own at least one pet.

“When you see how long we’ve had pets in our lives, and how important they are to us today, I think it’s amazing that the study of human-animal interactions is still so new,” says Dr. Sandra Barker, director of the Center for Human-Animal Interaction at Virginia Commonwealth University. “Researchers have only recently begun to explore this wonderful relationship and what its health benefits might be.”

It’s true that scientific study of the human-animal bond is still in its infancy. Several small or anecdotal studies have uncovered intriguing connections between human health and animal interactions. However, more rigorous follow-up studies have often shown mixed results.

“The general belief is that there are health benefits to owning pets, both in terms of psychological growth and development, as well as physical health benefits,” says Dr. James Griffin, a scientist at NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development. “But there have been relatively few well-controlled studies. That’s the state of the science, in a nutshell.”

This past year, NIH hosted several meetings to bring together leading experts in the field of human-animal interactions. The investigators discussed findings to date and ways to improve ongoing research.

Some of the largest and most well-designed studies in this field suggest that four-legged friends can help to improve our cardiovascular health. One NIH-funded study looked at 421 adults who’d suffered heart attacks. A year later, the scientists found, dog owners were significantly more likely to still be alive than were those who did not own dogs, regardless of the severity of the heart attack.

Another study looked at 240 married couples. Those who owned a pet were found to have lower heart rates and blood pressure, whether at rest or when undergoing stressful tests, than those without pets. Pet owners also seemed to have milder responses and quicker recovery from stress when they were with their pets than with a spouse or friend.

Several studies have shown that dog owners may get more exercise and other health benefits than the rest of us. One NIH-funded investigation looked at more than 2,000 adults and found that dog owners who regularly walked their dogs were more physically active and less likely to be obese than those who didn’t own or walk a dog. Another study supported by NIH followed more than 2,500 older adults, ages 71-82, for 3 years. Those who regularly walked their dogs walked faster and for longer time periods each week than others who didn’t walk regularly. Older dog walkers also had greater mobility inside their homes than others in the study.

Man’s best friend may help you make more human friends, too. Several studies have shown that walking with a dog leads to more conversations and helps you stay socially connected. And studies have clearly shown that people who have more social relationships tend to live longer and are less likely to show mental and physical declines as they grow older. “It’s hard to walk a dog and not have someone talk to you or interact with you, compared to walking alone,” says Barker.

Other research suggests that pet ownership may hold special benefits during childhood. “When children are asked who they talk to when they get upset, a lot of times their first answer is their pet,” says Griffin, an expert in child development and behavior. “This points to the importance of pets as a source of comfort and developing empathy. In fact, therapists and researchers have reported that children with autism are sometimes better able to interact with pets, and this may help in their interactions with people.”

Several research teams are examining the potential benefits of bringing specially trained animals into clinical settings. These animal-assisted therapies are increasingly offered in hospitals and nursing homes nationwide. Although there is little solid scientific evidence confirming the value of this type of therapy, clinicians who watch patients interacting with animals say they can clearly see benefits, including improved mood and reduced anxiety.

“You can see the difference it makes in so many of these patients when the dog is at their bedside,” says Berger, who works to relieve pain in patients with life-threatening illnesses at the NIH Clinical Center. “Our patients are often here for a long period of time. I think the dogs add a bit of normalcy to a very difficult situation. The dog will sit calmly, and the patients don’t have to talk to anyone. They can just pet. I think this helps with some of the suffering.”

Berger and Barker recently wrapped up a preliminary clinical study looking at how well animal-assisted therapy relieves distress in hospitalized cancer patients coping with pain. The data have not yet been analyzed, but the researchers hope it will serve as a launching point for future investigations.

“I think we’re just at the tip of the iceberg in terms of what we know about the human-animal bond and its potential health benefits,” Barker says. “This area is primed for a lot of research that still needs to be done.”